Drafting ellipsograph



. 1,635,270 Ju y 12 1927- D. GRIEVE DRAFTING ELLIPSOGRAPH Filed Jan. 31, 1927 Gnome thereby.

Patented July 12, 1927.

DAVID eamvn, or mrrnorr, MICHIGAN.

DRAITING ELLIPSOGBAPH.

Application Med January 31, 1997. Serial ll'o. 164,719.

My invention relates to a drafting instru ment and more especiall to an instrument for delineating ellipses s iown in'the accompanying drawings and particularly described in the following specification and claims.

This invention is designed as an improvement on the instrument shown in the Patent No. 1,415,5 l7' issuedrto me" May 11th, 1922, for a similar purpose.

One of the objects of the present invention is to produce an instrument simple in construction, of fewer parts, and less costly to manufacture.

A further object ofthe invention is to provide "a device having a wide range, andicapable of describing ellipses of relatively smaller and'greater major and minor axis than possiblewith the'instrumentto which reference has been made. 1

A further-object ott'he invention is to provide a device'in which the seribingpoint and the center post,--located at the intersection of the majorand minor axis,-are yieldably supported so that when the hand of the drafting rests" upon thevinst'rument the scribing point may readily follow" any possible irregularities in the plane surface supporting the paper on which the drawing is to be'exeouted. 1

WVith the foregoing: andother objects in View which will appear as the description proceeds, the invention further resides in. the combination and arrangement of parts and in the details of construction hereinafter described and claimed, it b'eing understood that changes may be made in the precise embodiment of the invention hereindisclosed without departing'fronr thespirit of the same.

In the drawings accompanying-this specificatio'n: I Figure l is a perspective view of the instrument with a portion or its swingingbeam broken away, showing'an ellipse partially described by the scribing point.

Fi ure 2 is a plan view ofthe instrument indideting in dotted lines; an ellipse {formed Figure 3 is a 'tragmentaryfside elevation on a relatively larger scale with'parts'in section to disclose tlieconstruction of the yieldable center post and the'hingedand slidable' connections between the different cooperating members of'the device.

Figure 4 1s a perspective-view of a detail showing 'a slidableadjustable member cartying a pen-point which is designed to replace the pencil scribing point, when it is desired to 111k a drawing.

Referring now to the letters of reference placed upon the drawings:

A denotes an L-shaped bracket arm with itsdownwardly extending leg A fitted with a transverse footpiece B, having spaced contact points B B for supporting the instrument upon a drafting board.

T e lower end of the leg A terminates in a wedge-shaped pointer A ,the contact edge ofwhich is on a plane with the contact points B B of the footpiece B and in use is placed on a line indicating the minor axis of the ellipse to be described.

Projecting from the forward end of the L-shaped bracket arm is a wedge-shaped extension plate A welded or otherwise secured to the bracket arm with lugs A A" at its flaring outer end secured to'a transverse bar C by rivets or other fastening means. I

I Rigidly secured to a bracket A projecting downwardly from the underside of the wedge-shaped plate A, is a bar D in spaced screw/F to secure it when adjusted to a swinging bracket arm H supporting a beam I, located below in spaced alignment with the bracket arm and rigidly secured to the latter.

'Thebracket arm H is pivoted to a slidable fixture J mounted upon the transverse "barC secured to the wedge-shaped bracket extension and is free to slide thereon.

' The bracket armH and fitting J are pivoted together by a screw J extending through a fiber washer sure the parts against seizing through an over-tight adjustmentof the screw.

Mounted upon the swinging beam I is a slidable fixture K, secured to the beam when adjusted by a thumb screw K on theend of a transverse bolt extending across the The fitting F is provided with a thumb J", employed to in' fixture-which is slotted longitudinally for a portion of its length as indicated at K whereby the thumb screw when adjusted may clamp the fitting securely to the swinging beam.

L is a tubular post tapped at its upper end to receive a screw-threaded plug M depending from the fitting K. N is a plunger housed in the post having an enlarged head N overlapping a shoulder in the post to limit its downward movement. The plunger N has also a downwardly projecting tubular stem l a into which is inserted a pencil or other scribing point,th'e pencil being held by the resilient action of the walls of the stem which are slotted (N at its lower end.

P is a coil spring bearing against the plunger at one end and the plug M at the other to maintain the scribing point at the limit of its movement but which is free to yield under the hand of the draftsman. Q is a center post screwed into the bar D and is recessed at its lower end to receive a yieldable plunger R,--fitted with a pivot needle S in its projecting end.

The wall of the tubular post Q is flanged as at Q to overlap a shoulder formed in the plunger R to limit its outer movement.

T is a spring coiled upon a stem of the plunger which bears against a shoulder on the latter and the wall of the post, the purpose being to provide a yieldable point under pressure of the draftsmans hand to adapt the device for work over irregular surfaces.

To set the instrument for describing an ellipse of given major and minor axes the intersecting lines X and Y are first laid out by the draftsman with the maximum length of the major and minor axis of the proposed ellipse indicated on the respective lines.

The swinging beam I is then turned in exact alignment with the bracket. bar A with the pivot needle S, supported by the post Q, at the intersection of the major and minor axis and with the wedge-shaped end A of the bracket arm A resting on the line of the minor axis. g

The fitting K on the swinging beam I is then adjusted so that the scribing point carried by the post L rests on the point inclicating the limit of the minor axis,.-being one-half of the width of the minor axis of the proposed ellipse, from the pivot needle .S at the intersection of the major and minor the limit of the major axis,-the same being cure the fitting F fixedly to the bracket H.

The instrument is now in condition to describe the proposed ellipse.

The swinging beam is then swung to a position adjacent and parallel with the L shaped bracket arm A, with the scribing point carried by the plunger N in contact with the paper at the point noted, the same being one-half the minor axis from the intersection of the major axis of the proposed ellipse.

The swinging beam is now turned so that its scribing point may delineate the proposed ellipse upon the paper,the scribing point in its journey traversing the points indicating the extreme major and minor axes of the ellipse. 7

To delineate an ellipse of greater length or breadth, the instrument has only to be adjusted with reference to the major and minor axis of the ellipse, in the manner indicated, to describe the proposed figure.

Having thus described my invention what I claim is:

1. In an instrument of the class described, a supporting bracket havingmeans adapted to register with a line representing one axis of an ellipse; a transverse bar secured to the projecting end of said supporting bracket; a bar parallel with and rigidly secured to the supporting bracket in spaced relation to the latter; a slidable element adapted to traverse the transverse bar; a

swinging beam provided with a bracket arm parallel to and spaced from the beam;

means for pivoting the slidable element carried by the transverse bar to the bracket of the swinging beam; a pair of elements pivoted to each other and respectively slidably mounted upon the bar rigidly secured to the supporting bracket and the bracket arm of the swinging beam, said slidable element carried by the bracket arm of the swinging beam having means for securing it to said arm when adjusted; a post rigidly secured to the bar carried by and parallel with said supporting bracket; and an adjustable slidable element fitted with a scribing point mounted upon the swinging beam including means for securing said fitting when adjusted to the swinging beam.

2. In an instrument of the class described, a supporting bracket having means adapted to register with a line representingone axis of an ellipse; means for supporting said bracket arm 1n spaced relation to the sur- 'face on which the ellipse is to be delineated;

a transverse bar secured to the projecting end of said supporting bracket; a bar parallel with and rigidly secured to the supporting bracket in spaced relation to the latter;

a slidable element adapted to traverse the transverse bar; a swinging beam provided with a bracket arm parallel to and spaced from the beam; means for pivoting the slid- 5 able element carried by the transverse bar to the bracket of the swinging beam; a pair of slidable elements pivoted to each other and respectively mounted upon the bar rigidly secured to the slidably supporting bracket and to the bracket arm of the swinging beam, the slidable element carried by the bracket arm of the swinging beam being provided with means for securing the slidable element to said arm when adjusted;

a post rigidly secured to the bar parallel with and carried bysaid supporting bracket;

a resiliently supported pivot mounted in said post; an adjustable slidable element mounted upon the swinging beam; a scribing point; resilient means for yieldably supporting said scribing point in the slidable element; and means for securing said slidable element when adjusted to the swinging beam. v

In testimony whereof, I sign this specification.

DAVID GRIEVEQ 

